When I put a DVD in the player it gives a "no Disk" message.

hi, if your dvd player is giving you disk error message or no disk message then the chances are the laser lense needs cleaning.

What you need to do is go to any big computer store and purchase a dvd lense cleaning disk, dont buy the cheapest one as they tend not to work so go for mid range or top end one.
Then all you need to do is put this disk into your dvd player and it will then clean the lense for you and should solve your problem.

If how ever you still have the problem then try different disk in it to ensure the dvd your trying is working ok if after doing this you still have the problem then the chances are the laser unit itself is no good and needs replacing.
The problem with this is unless your dvd player is built into the telly then the chances are it would be cheaper to go out and buy a new dvd player as the cost of repair would more than likely cost more than the cost of a new dvd player